From f17b11003fe384b49a7bf844824f23167b6095e0 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Sat, 30 Oct 2021 08:36:14 +0200
Subject: Add parsing of if expressions

---
 src/parser.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 83 insertions(+), 8 deletions(-)

(limited to 'src/parser.c')

diff --git a/src/parser.c b/src/parser.c
index 8a6c4ce..5551dd2 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -103,6 +103,7 @@ parse_lambda(Parser *parser, Errors *errors) {
             .line = tok.line,
             .col = tok.col,
         });
+        return NULL;
     }
 
     // Parse body.
@@ -119,23 +120,81 @@ parse_lambda(Parser *parser, Errors *errors) {
 }
 
 Object *
-parse_list(Parser *parser, Errors *errors) {
-    if (errors->n != 0) {
+parse_if(Parser *parser, Errors *errors) {
+    Token start = next_token(parser);
+    Object *obj_if = object_alloc(start, OBJ_TYPE_IF);
+
+    Token tok = peek_token(parser);
+    if (tok.type == TOKEN_RPAREN) {
+        error_push(errors, (Error){
+            .type = ERR_TYPE_PARSER,
+            .value = ERR_NOT_ENOUGH_ARGS,
+            .line = tok.line,
+            .col = tok.col,
+        });
         return NULL;
     }
+    obj_if->condition = parse_tree(parser, errors);
 
-    Token tok = peek_token(parser);
+    tok = peek_token(parser);
     if (tok.type == TOKEN_RPAREN) {
         error_push(errors, (Error){
             .type = ERR_TYPE_PARSER,
-            .value = ERR_UNBALANCED_PAREN,
+            .value = ERR_NOT_ENOUGH_ARGS,
             .line = tok.line,
             .col = tok.col,
         });
         return NULL;
     }
-    if (tok.type == TOKEN_LAMBDA) {
-        return parse_lambda(parser, errors);
+    obj_if->expr_true = parse_tree(parser, errors);
+
+    // Optional else expression.
+    tok = peek_token(parser);
+    if (tok.type == TOKEN_RPAREN) {
+        next_token(parser);
+        obj_if->expr_false = NULL;
+        return obj_if;
+    }
+    obj_if->expr_false = parse_tree(parser, errors);
+
+    tok = peek_token(parser);
+    if (tok.type != TOKEN_RPAREN) {
+        error_push(errors, (Error){
+            .type = ERR_TYPE_PARSER,
+            .value = ERR_TOO_MANY_ARGS,
+            .line = tok.line,
+            .col = tok.col,
+        });
+        return NULL;
+    }
+    next_token(parser);
+    return obj_if;
+}
+
+Object *
+parse_list(Parser *parser, Errors *errors) {
+    if (errors->n != 0) {
+        return NULL;
+    }
+
+    Token tok = peek_token(parser);
+    switch (tok.type) {
+        case TOKEN_RPAREN: {
+            error_push(errors, (Error){
+                .type = ERR_TYPE_PARSER,
+                .value = ERR_UNBALANCED_PAREN,
+                .line = tok.line,
+                .col = tok.col,
+            });
+            return NULL;
+        } break;
+        case TOKEN_LAMBDA: {
+            return parse_lambda(parser, errors);
+        } break;
+        case TOKEN_IF: {
+            return parse_if(parser, errors);
+        } break;
+        default: break;
     }
 
     Token start = previous_token(parser);
@@ -327,13 +386,29 @@ object_display(Object *obj) {
             printf(")");
         } break;
         case OBJ_TYPE_LAMBDA: {
-            printf("#{lambda( ");
+            printf("#{ lambda( ");
             for (size_t i = 0; i < array_size(obj->params); i++) {
                 object_display(obj->params[i]);
                 printf(" ");
             }
-            printf(")}");
+            printf(") ");
+            for (size_t i = 0; i < array_size(obj->body); i++) {
+                object_display(obj->body[i]);
+                printf(" ");
+            }
+            printf("}");
         } break;
+        case OBJ_TYPE_IF: {
+            printf("#{ if ");
+            object_display(obj->condition);
+            printf(" ");
+            object_display(obj->expr_true);
+            if (obj->expr_false != NULL) {
+                printf(" ");
+                object_display(obj->expr_false);
+            }
+            printf(" }");
+        };
     }
     return;
 }
-- 
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